Pneumatic motor for unit ventilators



Oct. 13,

R. P. .ROETTER PNEUMATIC MOTOR FOR UNIT VENTILATORS Filed Oct. 27, 1949 TRAVEL b I I I 3nventor ROBERT P. ROETTER 5 IO AIR PRESSURE (Ittorneg Patented Oct. 13, 1953 PNEUMATIC MOTOR FOR UNIT I VENTILATORS Robert P. Roetter, Gary, Ind., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application October 27, 1949,'Serial No. 123,851

14 Claims. (01. 137-790) The present invention relates to a pneumatic motor especially adapted for unit ventilators.

The most widely used control sequence for unit ventilators uses a cycle wherein the motor, ona rise in branch line pressure, first operates the fresh air damper to a predetermined minimum position and then, on a further rise in branch line pressure, hesitates or remains inoperative, and finally, upon a still further rise in branch line pressure, the dampers are gradually operated to a wide-open position. This function has been obtained in the past by picking up a second spring by the connecting linkage at the beginning of the hesitation part of the cycle which is preloaded to require a predetermined branch pressure to overcome it and thus start the third phase of the cycle. This arrangement has the disadvantage that a different pickup spring is needed for every difierent installation,

for its characteristics not only affect the hesitation part of the cycle but also determine the third or finishing part of the cycle. The present motor, by using three springs, can be readily adjusted for any installation without substituting any springs, hence it is a major object of the present invention to provide an improved pneumatic motor for unit ventilators.

It is a further object to provide a pneumatic motor for unit ventilators that is more compact than previous motors and that needs no exterior or supplemental springs to obtain a desired sequence of operation.

It is also an object to provide a pneumatic motor having an improved preloaded spring construction that is easily manufactured and very compact.

It is another object to provide a pneumatic motor that is easily adjusted to operate to a predetermined end position at a predetermined air pressure. g

It is a still further object to provide a pneumatic motor for unit ventilators wherein a hesitation cycle may b used or not depending upon the adjustment of the motor. 7

These and other objects will become apparent upon a study of the following specification and drawings wherein:

Figure 1 is an elevation view of the present motor with parts in section and parts broken tween movement of the operating lever of the 2 motor and branch line pressure, with different motor adjustments.

Figure 4 is a fragmentary view showing means for limiting relative motion of certain parts.

The present pneumatic motor is of the expansible chamber type and includes a flexible diaphragm Ill clamped between a lower rigid member H and an upper rigid member l2. Lower member II, in the nature of a base member, is a metal casting in the form of a shallow cup and includes an upper peripheral flange I3 and a lower attaching stud 14. In addition, a plurality of connection bosses [5 are formed around member H, each boss including tapped holes It for the connecting screws ll used to secure a connection block I8 in place, and another tapped hole l9 extends through said member for serving as an air connection. Hole I9 is adapted to align with a matching air passage in connection block [8 which also connects with tubing 26. A gasket 2| is normally used between block l8 and boss IE to prevent leakage and holes [9 not being used are closed by suitable threaded plugs or attached plates. Attaching stud [4 extends through an opening in mounting bracket 22 and is tightened in place by nut 23.

Upper member [2 includes a lower or body portion 26 having a peripheral flange 21 matching flange l3 and further has an upper support or bridging portion 28 extending across the tops of oppositely disposed supporting arms 29 and 30. Supporting arms 29 and 30 are formed with integral ears 3| and 32, respectively, and support member 28 includes a depending centrally located threaded member or portion 33, portions 28 and 33 having a hole 34 extending therethrough, said hole being aligned with the axis of said motor.

Flexible diaphragm I0 is molded in the form of a cup-like member of a heat resisting rubber-like material such as silicone rubber. This diaphragm is clamped between flanges l3 and 27 by suitable screws to form a motor chamber between said diaphragm and lower member II, this chamber being expansible upon a sufiicient increase in air pressure in said chamber. Motion of diaphragm Io is transmitted through a piston-like member 35 having an inclined side wall portion and a flat bottom portion, the side wall portion including extension arms 36 and 31 extending upwardly for connection to a forked operating lever. Forked operating lever 39 includes a slot 40 for connection to the linkage used in operating a unit ventilator, for instance, and also includes spaced fork members 4] and 42 pivoted at 43 and 44 to cars 3| and 32, respectively. Upwardly extending will now be followed. According to this curve, diaphragm I is able to start moving piston 35' and lever 39 at about 1% pounds per square inch pressure because, in raising members 50 and the force exerted by spring 48 is diminished to some extent. With movement started at 1 pounds per square inch pressure, it appears that the fresh air dampers will be driven to a 50% open position at 3 pounds per square'inch and then, on a further increase in pressure to 8 pounds per square inch, no furthertravel takes place, the initial portion of this curve being similar to H of the previous illustration and the hesitation portion corresponding to 12 of curve 10. Then, on the pressure building up sufiiciently to collapse spring 54, piston 35 will force member 56 against the compression of spring 54 along the line 75 of curve 14. However, if spring 54 is relied on to resist movement until arm 39 is driven to it upper extreme, then this extreme will be reached at a pressure of about 10 pounds per square inch, thereby shortening the throttling range of other devices which may be used with this apparatus. To avoid this shortening of the throttling range and to insure that arm 39 will be driven to its upper extreme only when the branch line pressure imposed on the motor reaches a predetermined value, such as 12 pounds per square inch, spring BI is adjusted by rotating nut 63 so that, at some portion of the travel of piston 35 and arm 39, the outwardly turned flange 49 of member 50 engages spring 6| so that further movement of member 50 upwardly will be against the combined resistances of springs 54 and 5!, the deflection characteristics now following line 16 of curve 14 and terminating in the 100% travel of the motor corresponding to a 12 pound per square inch branch line pressure.

If member 5! be adjusted to a still higher position, by rotating bolt 51 by head 58, so that the bottom of member 55 is not engaged by piston 35 until about 70% of the travel has taken place, it appears, according to curve 18, that movement will start at about 1 pound per square inch and the hesitation portion of the cycle will be reached at 3 pounds pressure, as before. Upon completion of the hesitation part of the cycle, and as the branch line pressure rises above 8 pounds per square inch, arm 39 again starts moving and will, if its motion is not modified, reach an extreme position at about 9 pounds per square inch pressure. To prevent this, spring BI is adjusted to be picked up at a somewhat lower position by flange 49 of cup 50. This is necessary because, as previously described, the latter part of the travel of piston 35 and arm 39 is against combined springs 54 and GI and, due to the present high setting of member 5|, spring 54 will not be compressed as much as in the previous example, hence it is necessary that spring 5| be compressed more than before if the proper end position is to be reached at the desired pressure. Then, due to spring Bl being engaged, and with the last portion of travel being against the combined effects of springs 54 and GI, line 19 of curve 18, in alignment with line 76, shows these characteristics and the end position of lever 39 is again reached at the desired 12 pounds per square inch pressure.

Obviously, by a still higher adjustment of members 50 and 5!, the hesitation part of the cycle may be displaced upwardly far enough to be inefiective so that 100% movement of lever 39 may be had in direct relation to increase in branch pressure. In this case the limiting position will be reached far below the aforementioned branch pressure but this latter arrangement is particularly desired for a sequence,

wherein the dampers are gradually opened wide and then the steam valve is gradually closed on a further rise in branch line pressure.

From the above description, it is seen that the present motor is useful for two of the most important unit ventilator cycles and it is adjustable to permit hesitation at any desired portion of motor stroke and still finish the cycle at a specified branch line pressure. With the present motor, the hesitation part of the cycle will always start at the same value of air pressure, the value depending upon spring 48, for this spring must be collapsed to its minimum length by engagement of piston 35 with cup 50' to start the hesitation. Likewise, the end of the hesitation part of the cycle normally depends upon the pressure required to overcome the preloading of spring 54, hence the hesitation part of the cycle, for any particular motor, is uniform for all normal adjustments.

An inspection of the present disclosure will reveal many substitutions and equivalents, hence the scope of this invention should be determined only by the appended claims.

I claim:

1. A pneumatic motor comprising a lower rigid member, an upper rigid member, a flexible diaphragm clamped between said members and forming an expansible chamber with one of said rigid members, an operating lever attached to the other of said rigid members, means including a piston-like member'operatively connecting said diaphragm to said lever, a preloaded spring means arranged to oppose movement of said diaphragm, said spring means including a pair of relatively movable members, a compression spring arranged between said relatively movable members for urging them apart axially, stop means for limiting their relative axial motion, means for adjustably attaching one of said relatively movable members to said other rigid member so that the other of said relatively movable members is normally spaced above the lowermost position of the piston-like member but may be caused to move by a predetermined movement of said diaphragm, another spring means arranged between the other of said relatively movable members and said piston-like member serving to bias said piston-like member toward its lowermost position, and an additional spring means arranged to be engaged by said other relatively movable member after a predetermined movement of said member, said additional spring means being attached to said other rigid member.

2. A pneumatic motor including a movable flexible diaphragm; an operating member movable by said diaphragm; and a preloaded spring means for opposing movement of said diaphragm beyond a predetermined amount, said spring means in-' cluding a pair of axially movable members, one of said members having a cup-like form, stop means attached to said axially movable member for limiting the relative axial movement of said axially movable members in a separating direc: tion, one of said members being movable by said diaphragm, and a spring compressed between.

3. A pneumatic motor including a movable fleX- I ible diaphragm; an operating member movable by said diaphragm; a preloaded spring means for pp in m vemen of sa d iaph a m, sa d spring mea s includ ng a pair or rela ve y movab e m mbe s, one of said members havin a diaphra m n a in po ti n, s op means to im tin the relative separating movement or said memb said one member being mo b e'by said diap ra a d a pring ompr ssed etw en sa m mbers and arranged to bias said membe s ap and adjustment means for said preloaded spring means comprisin threaded means or shifting said preloaded spring means toward or away from said diaphragm.

4. A pneumatic motor in lud ng a movable. flexible diaphragm; an operating member movable by said diaphragm; a preloaded spring m ans for opposing movement of said diaphragm, said pring means including a pair of axially m vably related members, one of said members havin a wer phra m engagin p rtion an an upp r flange portion, means for limiting the relative movement of said members in a separating direction, said one member being movable by said diaphragm, and a spring compressed. between said members and arranged to bias said members apart; adjustment means for said preloaded spring means comprising threaded means for shifting said preloaded spring means toward or away from said diaphragm; and additional spring means engageable .by theupper flange portion .of said one member after aid member has move a predetermined distance.

A pneumatic motor including a m vable flexible diaphragm; an operating member mov able by said diaphragm; a preloaded spr ng means for pposing movem nt of said diaph agm, said sprin means including a pair of movably related members, means jor limiting the relative axial movement of said members, one. of said members being movable by sai diaphram, and a spring compressed betweensaid members and. arranged to bias said members apart; adjustment means for said preloaded spring means comprising threaded means for shittingsaid preloaded spring means toward or away from sai d aphr m; a ditional spring means engageable by said one member movable by said diaphragm only after said member has moved a predetermined distance; and means for positioning said additional pring means omprising hreadedm ans axiall aligned with said first named threaded means.

6. A pneumatic motor .of the expansible cham-. ber type having a movable ,force exerting pistonlike member, first means for opposing movement of said member, second means for opposing movement of said member, said second means being adjustable in a manner to oppose said movement only after a predetermined movement of said member has taken place, movement against said second means being considered a second movement, and third resilient means for opposing movement of said member, said third means being engageable after a predetermined secondmovement of said member and causing a r istance o movement by a force which increases at a greater rate upon movement on said piston memberthan does either the first or second means.

'7. A pneumaticmotor of the .exloensible chamber type having a movable-force exerting pistonlike member, first spring means for opposing movement or said member, second sp ing concentric with said first sprin m ns 91 opposing movement of said member, said second spring means being adjustable ina manner to oppose said movement onlyafter apredetermined movement of saidmember has takenplace, andthird aetaiso pring means concentri i h sa d and c n s rin means or opp sin a pre eterm ned addi onal movement o a m mber. aid rd prin m ans coop at ng w th said seco d s rin mean o cause n inc ase in he sist nce t mo m nt of said m mb r a a ate r te th caused. .by e ther the first r econd sp in 8. A pneumatic motor having an expansible hamber ompr s g a f exible diaph gm and a rigid member enclosing one side of said diae ph g a upport member a tached o sa d ri id memb r, a p sto k m mb rra ged o be moved by said diaphrag sa p ton l k mem he havin a pa f upstanding arms, o me s attached to said support member, a forked opera e lever pivotally moun by said pivot means p vota v c nnect n said a ms to said forked lever for rotating said lever about said pivot means, a pair of slidably related members, spring m ans .for r n sai mem rs apart, stop means for limiting the relative separating movement of said members, one of said members being engageable by said pistonelike member, adjusting means for positioning said members to space said one member a predetermined distance from said piston-like member when said piston member is in its lowermost position, and an additional spring arranged to oppose movement of said piston-like member only after it has moved a predetermined distance, said additional spring having sufficient stiffness to require an increase in pressure in said chamber to move said pistonlike member against said additional spring means.

9. A pneumatic motor having an expansible chamber comprising a movable flexible dia-. phragm, e. piston-like member arranged to be moved by said diaphragm, an operating lever attached tosaid pistonelike member, a first spring arranged to oppose movement of said piston-like member by said diaphragm, a reaction member for said spring, a second spring, a reaction mem-.- ber for said second spri g, said reaction members being axially movably related, said second spring being arranged in compression between said reaction members, stop means for limiting the relative axial movement between said reaction memhere in a separating direction, said first reaction member including a piston-like member engage lng portion, and means for adjusting said second named ac o member to here adjus said first spring and the spacing of said piston-like membe en a i p r n of the firs nam eaction member and said piston member.

1.0. A pneumatic motor comprising an expansible chamber, a first spring arranged to resist expansi n f id c m e a p ad d s cond sp a an o re ist expansi n of a d ha be a d f such stiffness and preloedi -tha a pr dete min d n ase in the pressure o h air-supplied he motor m st t ke l ce efo e here is any deflection of the second sprin a third spring arranged to resist expansion of said chamber after a p edetermined expansion has talgen Place and of-sufficient stiffness to insure that the air pressure supplied to said motor must Ilse to a p edetermined value to expandsald chamber a predetermined total amount, and means for adjustably positioning saidrthird sprin to thereby determine the expansion required of said chamber ,before said third spring becomes effe tive.

11. A pneumatic motor having a frame and including an expansible chamber, a first spring arranged to resist expansion of said chamber, a pair of axially movable members, a second spring between said members for urging said members apart, said second spring being stiffer than said first spring, stop means coacting with said members for limiting the relative axial motion of said members in a separating direction, one of said members engaging said first spring, and threaded adjusting means coacting with the other of said members for positioning said pair of members, said one member being arranged to resist expansion of said chamber.

12. A pneumatic motor having a frame and including an expansible chamber, a first spring arranged to resist expansion of said chamber, a pair of axially slidably related members urged apart by a second spring, said second spring being stiifer than said first spring, stop means cooperating with said members for limiting the relative motion of said members in a separating direction, one or" said members engaging said first spring, threaded adjusting means coacting with the other of said members for positioning said pair of members, the one of said members being arranged to resist expansion of said chamber, and a third spring arranged to be engaged by said one member upon a predetermined expansion of said chamber.

13. A pneumatic motor comprising an expansible chamber formed by a rigid member and a flexible diaphragm, operating means movable by said flexible diaphragm, spring means for opposing movement of said diaphragm, means for mounting said motor comprising a stud member extending from said rigid member and arranged to coact with a suitable bracket, a plurality of air connection bosses disposed around the periphery of said rigid member and approximately equi- 10 distant from said stud member, air passages through each of said bosses to said chamber, an air connection means attached to one of said connection bosses in registry with its air passage, and sealing means for closing the openings in the connection bosses not being used.

14. A pneumatic motor having a compressed air connection and comprising a movable piston means and an operating member operable thereby, a first spring arranged to oppose an initial movement of said piston means, a second and preloaded spring means arranged to oppose movement of said piston means beyond said initial movement, mechanical means for adjusting the position of said second spring means, and an adjustable third spring arranged to resist movement of said piston means subsequent to defiection of said preloaded spring means, said motor being operable on a cycle wherein hesitation starts at an air pressure depending upon the rate of said first spring and its deflection at the end of said initial movement and ends at an air pressure determined by the force required to overcome said preloaded spring means.

ROBERT P. ROETTE-R.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,344,340 Fulton June 22, 1920 1,662,098 Anderson Mar. 13, 1928 1,825,637 Ricker Sept. 29, 1931 2,379,306 Larson June 26, 1945 2,396,448 Stevens Mar. 12, 1946 

